I don't know the specifics completely, but I do know you have it on a slanted track, and that there's a small wall about a third of the size of the boulder to stop it from going any further. No ropes are attached to the boulder, it was allowed to roll completely around.

I saw this animation at a theme park attraction 3 years ago lol so I'm just going by memory. I wish I could find video or pictures of it....